of four fundamental forces In nature, gravity is what we experience most directly – it’s what keeps our feet on the ground and the Sun in the sky. Yet we still cannot ascertain its exact strength. Since the 1980s, scientists have created more than a dozen measurements To calculate the exact value of gravity, and many of those numbers contradict each other.
So why is it so hard to find out how strong gravity Is?
One problem is that gravity is weak. Gravity feels strong because we constantly feel the Earth’s pull. But the gravitational force between any two objects in everyday life – or any two objects that can fit in an experimental laboratory – is exceptionally weak.
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“It’s weak, and you have to measure it against the background of Earth’s gravitational field,” stephan schlammingera physicist at the National Institute of Standards and Technology told Live Science. “If we measure gravity, we have to use everyday objects, because these are the only objects where we know the mass. In the laboratory you basically have to use two very controlled masses, bring them together, and measure the force between them.”
in one April 2026 studySchlamminger and colleagues repeated an exact experiment to determine the strength of gravity and calculated a value different from the previous result. They used 13 tons (12 metric tons) of mercury to run their experiment, but even so, “the change in the gravitational field was only one millionth of the change we have here from local gravity,” he said.
The team’s measured value was 6.67387×10-11 m3kg-1S-2Which was 0.0235% less than the previous result – a small difference in everyday terms, but significant in the field of metrology.
Christian RothleitnerCo-author, a physicist at the German National Metrology Institute comprehensive review All gravity measurements were made with Schlamminger in 2017, but were not included in the new study.
“This small force has to be quantified to six or more decimal places,” Rothleitner told Live Science in an email. “This is equivalent to trying to measure the weight of 7 human cells.”
Physics, Engineering and Psychology
One explanation for the discrepancy in values may be that all measurements are so vague that the true value lies somewhere in them. But each experiment reports a small margin of error, and those ranges do not overlap.
Schlamminger believes there are three possible reasons for this.
“I have this handy acronym: It’s PEP: the P stands for physics, the E stands for engineering, and the second P stands for psychology,” Schlamminger said. “This has been resolved based on enthusiasm.”
The least likely explanation, he said, is physics: There may be some element of physics that scientists don’t yet understand. Just as general relativity As scientists expand their understanding of gravity, there is another area of physics yet to be discovered.
The fabric of spacetime is an important concept in the theory of general relativity, because the fabric can be distorted by gravity.
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“I think it’s a remote possibility, but we shouldn’t rule it out,” Schlamminger said.
Again, there is the engineering explanation: each experiment uses a slightly different setup, resulting in different values. Some people use a torsion balance, a device that senses small forces by measuring the twist of a small fiber. Others use pendulums or freely falling objects. Each approach has its own potential sources of error, and those errors are difficult to reconcile with the gravity signal.
Rothleitner said, “I personally do not believe that the reason lies in physics, but rather in measurement technology.”
Human error is another part of the engineering explanation. “This type of experiment requires expert knowledge in many areas of physics and measurement technology,” Rothleitner said. “You can’t be an expert in all of those areas. This type of measurement is at the cutting edge of metrology.”
The most likely possibility is psychology-related, Schlamminger said.
“There’s a driver for these guys who scale these numbers to give them really small uncertainties” — that is, margins of error — “because that’s what makes them famous,” Schlamminger said. “Because there is pressure, the uncertainties can become a little too small, and that’s why they don’t agree with each other.”
However, in the end, the exact measurement of gravity does not matter. we know the product The mass of is G times the mass of Earth, and this is enough for practical applications such as launching rockets into space. Maybe that’s all we need right now.
“The value of Newton’s gravitational constant is of academic interest,” Rothleitner said. “If it were different, nations would put more effort into determining it better.”
However, Schlamminger still finds it exciting. “We live in a society where we think everything is invented,” he said. “But if you look, there’s still Terra Incognita. There are still problems, and the problems may be small, but they are still problems that we can solve and contribute to and find fascinating and interesting. And this is one of those problems.”
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